Innate immunity: Pattern recognition receptors and signalling Flashcards
Describe what Candida albicans can cause
Fungus infection = can cause severe septic shock
Certain pop of individuals = more susceptible
Fungus activates alternative pathway of complement
Describe gros lab experiment set up
Study compared genetics of 2 strains of mice = one susceptible and one relatively resistant to infection
Analysis of genomes showed that susceptible strain had deletion in gene that coded for c5a
Mice of each strain infected with c albicans then load of fungus determined
What are observed results of gros research lab activity
Susceptible mice have higher load of c albicans
What are CONCLUSIONS of gros research lab activity
C5a needed to clear c albicans = functional role important
WHAT do pathogens have
Specific molecular patterns that support their lifestyle = pamps
What are pamps recognized by
Prrs = on host cells, in host cells (can be intracellular) and are host soluble proteins
Range of locations = ensures that cells can recognize pamps of virtually any pathogen
What is also recognized by prrs
Damps = damage associated molecular patterns
Which cells have prrs
All types of myeloid wbcs
Subset of lymphoid cells = some T cells, B cells and nk cells = part of innate immune response
Describe prrs expressed by some other cell types
Those common exposed to infectious agents = epithelial cells of skin and mucosal tissues and endothelial cells that line blood vessels leading to production of antimicrobial substances
What is expressed by most if not all cells in body
Cytosolic sensors of viral nucleus acids
Where are prrs located
At diff sites depending on pamp they recognize = cell surface, intracellular or secreted
Name groups of prrs
Toll like receptors = tlrs
Nod like receptors = nlrs
Rig I like receptors = rlrs
C type lectin receptors = clrs
Ficolins, mannose binding lectins, c1q
Others
What do prrs activate
Signalling pathways = contributing to innate/inflammatory response
Compare cell surface bc intracellular prrs
Bind on surface = pamp on surface = lipopeptides, flagellin, lps
Intracellular = binds nucleic acids mainly = rna and dna
Describe toll like receptors
Extracellular= bind bacteria, parasites, fungi = cell wall, gram neg bacteria
Intracellular = still membrane bound to vesicle or endoscope =more viral, nucleic acids
Intracellular vs Extracellular receptors = logic behind corresponding pamps = location helps determine what binds
What does tlr binding of pamps do
Activates signalling pathways
Diff tlrs recruit diff adaptor proteins = link protein binding partners together and facilitate large signaling complexes
Diff adaptor proteins lead to diff events
Name and describe adaptor proteins/events
Nf-kB transcription factor activation
Interferon regulating factor = irf pathways
Map kinase pathway downstream transcription factors = ap-1
What are transcription factors
Nf-k-B,irf and ap-1 = tfs
In cytoplasm —> activated —> nucleus
End result of signalling and gene expression
Signalling leads to activation of tfs —> transcription of innate immune/pro-inflammatory genes
Once genes expressed = have specific impacts
Describe signalling cascade
Signalling cascade triggered = involves many proteins
Phosphorylation = key event,addition of phosphoryl group to molecule = leads to activation of tfs, translocate into nucleus to activate gene expression
What are key molecules
Adaptor proteins = myD88, TRIF
Transcription factors = irf3/7, nf-kb, ap-1
Name and describe all general features of signal transduction
Ligand induced receptor dimerization —> recruitment/activation of kinases and adaptors —> Second messenger = through phosphorylation, ca, camp, dag, etc —> activation/nuclear translocation of tfs —> Changes in gene expression —> Post transcriptional or translational mods —> Functional response —> secreted out of cell —> functional
Describe central dogma
Dna —transcription—> mRNA —translation—> protein
Each gene has promoter
Tfs bind specific sequences on promoter = response element
Recruits rna polymerase =
Transcription begins
Describe what western blot can detect
Proteins and their phosphorylation =
When recruit/activate kinase and adaptor and when second messengers
Describe what can see activation / nuclear translocation of transcription
Proteins and their phosphorylation can be isolated form nucleus and detected and their binding to promoter regions can be determined
What is rt pcr used for
Detect mRNA = when changes in gene expression
When use northern bblot
mRNA stability/splicing can be detected and determined - pre or post cleavage = when post transcriptional or translational mods
When can Extracellular protein be detected
After secreted out of cell = when have functional response
Describe c type lectin receptors = what type
Membrane receptros = on surface
Describe c type lectin receptors = what bind
Binds carbohydrates on pathogen and some allergens = peanut, dust mite proteins
Describe c type lectin receptors = cascade
Activated tyrosine kinases trigger signalling cascade =
Card adaptor protein
Irf5 activation = tf
Map kinase pathways activation = result in activation of ap-1 and nf-kB = tfs go into nucleus and
Induce expression of inflammatory cytokines
Describe rig I like receptors = function
Function as cytosolic prrs = inside cell
Describe rig I like receptors = detect
Recognize viral double stranded rnas and certain structured single stranded rna = mainly viral
Describe rig I like receptors = mavs
Mitochondrial antiviral signalling protein = card connects rig I to mavs
Describe rig I like receptors = signalling pathways
Mavs trigger signalling pathways that activate irfs and nf-kb = tfs
Then translocation and transcription
What does nod like receptors stand for
Nucleotide oligomerization domain
Describe nlrs function
Cytosolic prrs
Some floating or anchored = on endosome
Describe nlrs recognize
Peptidoglycan from bacterial cell wall - must enter Cytosol
When phagocytosis= in phagosome = chop up, so pieces peptidoglycan can be recognized by nlrs
Describe nlrs = triggers what
Nf-kb and ap-1 and irf signalling = tfs
Describe nlrs = activates what
Caspase 1 protease
Cleaves il-1beta/il-18 into active forms = for release of pro inflammatory cytokines
= POST TRANSLATIONAL MOD
Describe nlr post translational modification
Pro cytokines = pro-il-1beta + pro-il-18, active caspase 1 cleaves and makes ready to be secreted = il-1beta and il-18
Describe prr signalling pathway mods = which 2 types
phosphorylation and ubiquitination
Describe ubiquitination
Process of attachment of one or many subunits of ub to target protein = can mediate their formation for further signalling = activation sometimes but mostly degradation of protein
What can prr signalling pathways result in
Post transcriptional and post translational mods
What is ultimate goal prr signalling
To Carry out function = cytokines, other signalling molecules
